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1
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Diffusive Propagation of Phonon Beams in Yttrium Aluminum Garnets Containing Substitutional Rare Earth Atoms

100%
Ivanov S., Khazanov E., Paszkiewicz T., Taranov A., Wilczyński M.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
381-386
EN
The diffusive maxima of phonon signals are studied for a number of solid solutions of rare earth atoms in yttrium aluminum garnets. The used exact formula for the diffusion constants allows for qualitative discussion of the obtained results. The established energy of phonons, forming the diffusive maximum of phonon signal of the temperature T_{H} arriving at the bolometer, ranges from 3.2k_{B}T_{H} to 4.2k_{B}T_{H}, which is in reasonable agreement with the existing estimations. The qualitative analysis allows us to estimate the contribution, made by the rare earth ions occupying the octahedral positions of the sixfold oxygen coordination, to the scattering of phonons due to lattice imperfections in yttrium aluminum garnets.
2
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Combined (ZnSe/MgS)/ZnCdSe Bragg Reflectors Grown Using ZnS as a Sulphur Source

100%
Solnyshkov D., Sorokin S., Sedova I., Toropov A., Ivanov S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
873-877
EN
We report on MBE growth and study of optical and structural properties of (ZnSe/MgS)/ZnCdSe distributed Bragg reflectors with λ=520 nm and R_{max}=97%. The samples were grown pseudomorphically on GaAs substrate using ZnS as a sulphur source. Scanning electron microscopy, X-ray diffraction, and optical measurements showed good optical and structural characteristics of the Bragg reflectors.
3
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Optical Absorption in Periodic InN:In Structures

100%
Plotnikov D., Shubina T., Jmerik V., Semenov A., Ivanov S.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
191-196
EN
Optical absorption measurements were exploited to study periodic InN:In structures grown by plasma-assisted molecular beam epitaxy with the thickness of the metallic inclusions varied from 2 to 48 monolayers. We demonstrate that the observed higher-energy shift of an effective absorption edge may be due to In depletion of the InN matrix via the coalescence of In into large clusters, accompanied by the respective higher-energy shift of the Mie resonance. The relevant uncertainty in the optical gap of InN is discussed.
4
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CdSe Layers of Below Critical Thickness in ZnSe Matrix: Intrinsic Morphology and Defect Formation

86%
Sedova I., Shubina T., Sorokin S., Sitnikova A., Toropov A., Ivanov S., Willander M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
519-525
EN
Three main stages of the intrinsic morphology transformation of MBE grown CdSe fractional monolayers in ZnSe with increase in their nominal thickness w in the 0.1-3.0 monolayer range were found using both structural and optical characterization techniques. Emergence of the extended (15-30 nm) CdSe-enriched quantum-dot-like pseudomorphic islands at w>0.7 monolayer with the density increasing up to 2.5×10^{10} cm^{-2} at w=2.8 monolayer is clearly displayed in the optical properties of CdSe fractional monolayer nanostructures. The below critical thickness CdSe fractional monolayers having extremely high quantum efficiency can be very perspective as an active region of ZnSe-based blue-green lasers.
5
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Growth Control of N-Polar GaN in Plasma-Assisted Molecular Beam Epitaxy

86%
Mizerov A., Jmerik V., Kaibyshev V., Komissarova T., Masalov S., Sitnikova A., Ivanov S.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1253-1258
EN
The paper reports on plasma-assisted MBE growth of good quality N-face GaN layers directly on c-Al₂O₃ substrates. Growth kinetics under different growth conditions (substrate temperature, Ga to activated nitrogen flux ratio, etc.) during deposition of GaN(0001) and GaN(0001̅) both by the ammonia-based MBE or plasma-assisted MBE was studied. It was found that atomically smooth surface of 1 μm thick GaN(0001̅) films can be achieved by plasma-assisted MBE at the relatively high substrate temperature T_S ≈ 760°C and Ga to activated nitrogen flux ratio F_Ga/F_N* ≈ 1.8.
6
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Optically Pumped Low Threshold ZnSe Based Lasers with 2.8 ML CdSe Active Region

86%
Sorokin S., Toropov A., Shubina T., Lebedev A., Sedova I., Ivanov S., Waag A.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
539-544
EN
Room-temperature optically pumped (Zn,Mg)(S,Se)/(Zn,Cd)Se laser structures have been grown by molecular beam epitaxy. Using of alternatively-strained short-period superlattice waveguide results in low threshold power density values over the whole blue-green (470-520 nm) wavelength range. Incorporation of CdSe fractional monolayer active region provides more than fourfold further decrease in threshold with respect to quantum well laser structure. Optical and structural properties of laser structure with 2.8 monolayer CdSe are discussed in detail.
7
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InSb Quantum Dots in an InAsSb Matrix Grown by Molecular Beam Epitaxy

86%
Semenov A., Solov'ev V., Meltser B., Lyublinskaya O., Terent'ev Y., Sitnikova A., Ivanov S.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
859-865
EN
We report on molecular beam epitaxy of InSb insertions in InAs and InAsSb matrices, emitting at wavelengths beyond 4μm. Different growth techniques for deposition of InSb quantum dots in the 1-2 monolayer range of the InSb nominal thickness, namely conventional molecular beam epitaxy and migration enhanced epitaxy, as well as different matrices (InAs and InAsSb) have been employed for increasing the emission wavelength of the InSb/InAs nanostructures. The formation of InSb quantum dots has been studied in situ using reflection high energy electron diffraction and ex situ by using transmission electron microscopy. The peculiarities of In(Ga)AsSb alloys growth and compositional control are also discussed. Bright photoluminescence up to 4.5μm has been observed at 80 K.
8
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CdSe/ZnCdSe Quantum Dot Heterostructures for Yellow Spectral Range Grown on GaAs Substrates by Molecular Beam Epitaxy

86%
Gronin S., Sorokin S., Kazanov D., Sedova I., Klimko G., Evropeytsev E., Ivanov S.
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vol. 126
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issue 5
1096-1099
EN
This paper reports on theoretical calculations and fabrication by molecular beam epitaxy of wide-gap II-VI heterostructures emitting in the "true" yellow range (560-600 nm) at room temperature. The active region of the structures comprises CdSe quantum dot active layer embedded into a strained Zn_{1-x}Cd_{x}Se (x=0.2-0.5) quantum well surrounded by a Zn(S,Se)/ZnSe superlattice. Calculations of the CdSe/(Zn,Cd)Se/Zn(S,Se) quantum dot-quantum well luminescence wavelength performed using the envelope-function approximation predict rather narrow range of the total Zn_{1-x}Cd_{x}Se quantum well thicknesses (d ≈ 2-4 nm) reducing efficiently the emission wavelength, while the variation of x (0.2-0.5) has much stronger effect. The calculations are in a reasonable agreement with the experimental data obtained on a series of test heterostructures. The maximum experimentally achieved emission wavelength at 300 K is as high as 600 nm, while the intense room temperature photoluminescence has been observed up to λ =590 nm only. To keep the structure pseudomorphic to GaAs as a whole the tensile-strained surrounding ZnS_{0.17}Se_{0.83}/ZnSe superlattice were introduced to compensate the compressive stress induced by the Zn_{1-x}Cd_{x}Se quantum well. The graded-index waveguide laser heterostructure with a CdSe/Zn_{0.65}Cd_{0.35}Se/Zn(S,Se) quantum dot-quantum well active region emitting at λ =576 nm (T=300 K) with the 77 to 300 K intensity ratio of 2.5 has been demonstrated.
9
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Cobalt Additives Influence on Phase Composition and Defect Structure of Manganese Dioxide Prepared from Fluorine Containing Electrolytes

86%
Sokolsky G., Ivanov S., Ivanova N., Boldurev Y., Kobulinskaya O., Demchenko M.
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issue 1
86-90
EN
Manganese dioxide samples were prepared from fluorine containing electrolytes with additives of Co^{2+} ions. Atomic absorption spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis were the methods of the samples characterisation. Manganese dioxide at the presence of cobalt forms nanosized ramsdellite structure crystallites of mostly needle-like morphology with significant content of hydroxide groups. The main phase state in manganese dioxide samples obtained at the presence of cobalt is γ-MnO_{2} with ramsdellite structure and low content of intergrowth defects. The sample doped both with lithium and cobalt can be indexed to a hollandite-type structure (tetragonal; space group I4/m) of α-MnO_{2}.
10
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Optical and Structural Properties of GaAs/AlGaAs Quantum Wells Grown by MBE in the Vicinity of As-Rich-GaAs/ZnSe Heterovalent Interface

86%
Klimko G., Evropeytsev E., Sitnikova A., Gronin S., Sedova I., Sorokin S., Ivanov S.
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vol. 126
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issue 5
1184-1186
EN
The studies of structural and optical properties of molecular beam epitaxy grown pseudomorphic hybrid structures with AlGaAs/GaAs quantum well placed closely to the GaAs/ZnSe heterointerface are presented. The interfaces were formed in different ways (Zn or Se initial GaAs surface exposure, different growth temperature and ZnSe growth mode) on As-rich c(4×4) and (2×4) GaAs surfaces. It has been demonstrated that the photoluminescence intensity from the near-heterointerface GaAs QW is influenced most significantly by the procedure of ZnSe growth initiation. The bright photoluminescence (77 K) from the near-interface GaAs quantum well is observed if the Se-decoration procedure is used during the GaAs/ZnSe heterointerface formation on (2×4)As GaAs surface. It reduces noticeably if the GaAs reconstruction changes to c(4×4)As and disappears completely when Zn pre-exposure of GaAs surface is used. These effects are discussed in terms of different ratio of Ga-Se and As-Zn bonds at the GaAs/ZnSe heterointerface resulting in different band offsets and/or uncompensated built-in electric fields.
11
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Magneto-Optical Studies of Narrow Band-Gap Heterostructures with Type II Quantum Dots InSb in an InAs Matrix

73%
Mukhin M., Terent'ev Y., Golub L., Nestoklon M., Meltser B., Semenov A., Solov'ev V., Sitnikova A., Toropov A., Ivanov S.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
868-869
EN
Magneto-optical properties of type II heterostructures with InSb/InAs quantum dots has been studied at external magnetic field applied in the Faraday geometry. The emission polarization degree can be changed in the range from 100% σ-minus to 10% σ-plus due to excitation intensity and temperature variation. The detailed calculation of the band structure within a tight-binding approximation is presented. The simulation of the experimental data reveals that the oscillator strength of the optical transitions involving electrons with the spin oriented along and opposite to the magnetic field vector differs by approximately 1.8 times in the heterostructures under study.
12
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Effective Green Semiconductor Lasers with Multiple CdSe/ZnSe QD Active Region for Electron Beam Pumping

73%
Gronin S., Sorokin S., Sedova I., Kop'ev P., Ivanov S., Zverev M., Gamov N., Peregoudov D., Studionov V.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1115-1122
EN
The characteristics of ZnSe-based electron beam pumped semiconductor lasers are presented in detail. The laser structures consist of a 0.6 μm thick superlattice waveguide centered with ten equidistantly placed CdSe/ZnSe quantum dot active layers. The maximum light output pulse power of 12 W per facet at room temperature along with an extremely high quantum efficiency of ≈8.5% were obtained at an electron beam pumping energy of 23 keV (the laser wavelength is of 542 nm). The calculations of a spatial distribution of non-equilibrium carrier concentration within the semiconductor structures under electron beam pumping are presented. The possible ways of further improvement of laser efficiency are discussed.
13
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AlGaN Quantum Well Heterostructures for Mid-Ultraviolet Emitters with Improved Room Temperature Quantum Efficiency

73%
Shevchenko E., Toropov A., Nechaev D., Jmerik V., Shubina T., Ivanov S., Yagovkina M., Pozina G., Bergman J., Monemar B.
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vol. 126
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issue 5
1140-1142
EN
We report on optical studies of exciton localization and recombination kinetics in two single 2.2 nm thick Al_{x}Ga_{1-x}N/Al_{x+0.1}Ga_{0.9-x}N quantum well structures (x=0.55 and 0.6) grown by plasma assisted molecular beam epitaxy on a c-sapphire substrate. Strong localization potential inherent for both the quantum well and barrier regions results in merging of the quantum well and barrier emission spectra into a single broad line centered at 285 nm (x=0.55) and 275 nm (x=0.6). Time-resolved photoluminescence measurements revealed surprising temperature stability of the photoluminescence decay time constant ( ≈ 400 ps) relevant to the recombination of the quantum well localized excitons. This observation implies nearly constant quantum efficiency of the quantum well emission in the whole range from 4.6 to 300 K.
14
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Content available

Cd(Mg)Se Single Layers and CdSe/CdMgSe Heterostructures Grown by Molecular Beam Epitaxy on InAs(001) Substrates

73%
Kaygorodov V., Sorokin V., Sedova I., Nekrutkina O., Sorokin S., Shubina T., Toropov A., Ivanov S.
Acta Physica Polonica A
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2001
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vol. 100
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issue 3
443-450
EN
We report on molecular beam epitaxy of CdSe/CdMgSe heterostructures on InAs(001) substrates and studies of their optical and structural properties. The CdMgSe energy gap versus composition dependence is determined. The zinc-blende MgSe band-gap energy and optical bowing parameter are estimated to be 4.05 eV and 0.2 eV, respectively. The CdSe quantum wells embedded into CdMgSe barriers demonstrate intense photoluminescence. Effective mass approximation calculations of electron-heavy hole optical transitions in CdSe quantum well are in a good agreement with the experimental data obtained.
15
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Structural and Optical Properties of Alternately-Strained ZnS_{x}Se_{1-x}/CdSe Superlattices with Effective Band-Gap 2.5-2.6 eV

73%
Evropeytsev E., Sorokin S., Gronin S., Sedova I., Klimko G., Sitnikova A., Baidakova M., Ivanov S., Toropov A.
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vol. 126
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issue 5
1156-1158
EN
We report on design and fabrication of alternately-strained ZnS_xSe_{1-x}/CdSe short period superlattices with the effective band-gap 2.52, 2.58, and 2.61 eV and the total thickness ≈300 nm. Transmission electron microscopy, X-ray diffraction, and photoluminescence measurements reveal negligibly small density of misfit dislocations in the superlattices. The investigation of carrier transport along the superlattice growth axis, performed by the photoluminescence measurements of a superlattice with one enlarged quantum well, confirms efficient Bloch-type transport at temperatures above ≈ 100 K. Such superlattices look promising for the applications as a material for the wide band-gap photoactive region of a multi-junction solar cell comprising both III-V and II-VI materials.
16
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Micro-Photoluminescence Studies of CdSe/ZnSe Quantum Dot Structures Grown under Different Conditions

73%
Rakhlin M., Sorokin S., Sedova I., Usikova A., Gronin S., Belyaev K., Ivanov S., Toropov A.
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EN
We report on comparative studies of CdSe/ZnSe quantum dot structures grown by molecular beam epitaxy either with or without predeposition of a sub-monolayer-thick CdTe layer (stressor). Also we consider the structure grown in a thermal activation mode. Emission properties of individual quantum dots are investigated by micro-photoluminescence spectroscopy using 500 nm apertures opened in a non-transparent gold mask. The density of emitting quantum dots and the spectral width of the single-dot emission lines are estimated.
17
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Optical Studies of Thermally Activated Vertical Hole Transport in ZnCdSe/ZnSSe Superlattice

73%
Lebedev A., Sorokin S., Toropov A., Shubina T., Il'inskaya N., Nekrutkina O., Ivanov S., Pozina G., Bergman P., Monemar B.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
421-426
EN
Miniband transport in alternatively-strained ZnCdSe/ZnSSe short period superlattices is investigated using a structure with an enlarged quantum well. Temperature dependences of time-resolved and continuous wave photoluminescence have been measured, demonstrating an efficient temperature-induced vertical hole transport. A quantitative description is given for the carrier kinetics in these structures.
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